1. Field of the Invention
This invention relates to a fossil fuel-fired, fluid heating apparatus having a fluid container disposed within a combustion chamber in which combustion air is drawn into the combustion chamber through a combustion air inlet opening and combustion product gas is drawn through the combustion gas chamber and exhausted whereby the pressure within the combustion chamber is slightly less than atmospheric. More particularly, this invention relates to a natural gas-fired, induced-draft fryer.
2. Description of Prior Art
Known deep-fat fryers, such as are taught by, for example, U.S. Pat. No. 4,397,299, U.S. Pat. No. 4,602,612, U.S. Pat. No. 4,913,041, U.S. Pat. No. 4,848,318, U.S. Pat. No. 3,712,289, U.S. Pat. No. 3,217,704, and U.S. Pat. No. 4,905,664 are forced air systems in which combustion air is blown into the burner for heating the cooking medium with a fan, causing the burner system to operate at a slightly positive pressure. As a result, after continued use, these positive pressure fryers often develop leaks around the gasketing at the burner/frypot interface and elsewhere within the flue gas passage and, thus, constituting a substantial reliability weakness. These leaks result in high temperature flue gases, on the order of 700.degree. F.-900.degree. F. leaking into the fryer cabinet area, adversely affecting electronics and other temperature-sensitive components therein.
This invention essentially eliminates the leakage of flue gases into the fryer cabinet area and, thus, increases fryer reliability, by providing a suction on the flue gases, thereby causing the burner system to operate at a slightly subatmospheric pressure. As a result, any leakage that does occur will be into the combustion system and not into the fryer cabinet area.
U.S. Pat. No. 4,945,890 teaches an induced draft warm air furnace having a radiant infrared burner in which the use of an induced draft is indicated to eliminate the possibility of combustion gases leaking out of the combustion chamber or heat exchanger thereof. Similarly, U.S. Pat. No. 4,993,402 teaches a fuel-efficient, rapid, water heating module in which an induction draft fan is employed for causing a flow of combustion gases from the burner cavity, through the tank flue, the preheater jacket, and out to an external flue. In both apparatuses, the combustion chambers are sealed in a manner which prevents the inflow of secondary air into the combustion chamber due to operation of the devices at subatmospheric conditions within the combustion chambers. That is, the fuel and primary combustion air are premixed prior to introduction into the combustion chamber and subsequent combustion thereof.